Lysozyme is a O-glycosyl hydrolase produced as a defensive mechanism against bacteria by many organisms. The enzyme causes the hydrolysis of bacterial cell walls by cleaving the glycosidic bonds of peptidoglycan; an important structural molecule in bacteria. After having their cell walls weakened by lysozyme action, bacterial cells lyse resulting from osmotic pressure.
Lysozyme occurs in many organisms such as viruses, plants, insects, birds, reptiles and mammals. In mammals, Lysozyme has been isolated from nasal secretions, saliva, tears, intestines, urine and milk. The enzyme cleaves the glycosidic bond between carbon number 1 of N-acetylmuramic acid and carbon number 4 of N-acetyl-D-glucosamine. In vivo, these two carbohydrates are polymerized to form the cell wall polysaccharide.
Bacteria against which Lysozyme has shown effectiveness include Clostridium butyricum, Clostridium sporogenes, Clostridium tyrobutyricum, Listeria monocytogenes. 
The lytic action of egg white lysozyme protein is presently being exploited in two markets.
In cheese production, Lysozyme has been found effectively destructive on the vegetative forms of Clostridia bacteria and specifically Clostridium tyrobutyricum. These bacteria have been found to survive the normal heat treatment of milk used in the production of cheese and later propagate to cause late blowing. Late blowing is the formation of gasses during butyric fermentation occurring in the course of cheese maturation. The effects of the unwanted gas formation can be: faults in texture through the development of irregular-shaped eyes; or obvious undesirable tastes and smells; and finally, the cheese block may completely break apart. With the use of Lysozyme in the milk culture, the production and curing of the cheese may be carried out without concern for butyric fermentation causing late blowing effects. This has led to the wide-spread use of Lysozyme in European cheese production, particularly in the manufacture of medium and long-term ripening cheese. The recommended dosage is 0.2 lbs/1000 gallons milk. The lysozyme must be added after the last heat treatment due to heat instability, and as early as possible before rennet is added due to protease sensitivity.
In pharmacology, Lysozyme's natural function in biological liquids is to attack bacteria foreign to the body. Many bacteria that invade the body through any typical route-eyes, mouth, nose and wounds are challenged with the human immunological system, of which Lysozyme is a critical part. This anti-infectious activity has been exploited in the pharmacological industry by producing pharmaceutical tablets and capsules containing this egg white derived protein. It is also an important component in eye drops, toothpaste and throat lozenges. Potential uses for Lysozyme are varied. Successful results have been determined in cancer research and veterinary applications. As a food preservative, Lysozyme is a natural, organic alternative to many potential carcinogens. Lysozyme's use in baby food applications as well as in animal feed has shown positive results. The potential for this egg white derived enzyme is diverse and research and development on future applications is ongoing.
A GH25 lysozyme has been reported from Chalaropsis (Felsch J W, Ingagami T, and Hash J H. (1975) The N,O-Diacetylmuramidase of Chalaropsis species; V The complete amino acid sequence. JBC. 250:10 pp 3713-3720).
Hen egg white lysozyme which is the primary product available on the commercial market, does not cleave N,6-O-diacetylmuramidase in e.g. Streptococcus aureus cell walls and is thus unable to lyse this important human pathogen among others.
New polypeptides having lysozyme activity is therefore desired.